Always-on cameras are cameras that can continuously capture images at a given sampling rate or that are always available for capturing images, which can be used in various applications on a mobile device, such as life-logging, gesture identification/recognition, indoor-outdoor inference, and more. As processing and storage capabilities of mobile devices (e.g., mobile phones, tablets, head- or body-mounted cameras, head-mounted or heads-up displays, etc.) continue to increase, so too does the potential functionality of such always-on cameras. However, the power requirements of always-on cameras can be high relative to other sensors, and many images captured by always-on cameras have little or no value.